Uneven Sprinkler Coverage: How to Find and Fix Dry Spots and Soggy Areas

Last updated: October 2026 · Written by the LawnVibe editorial team.

Dry, brown patches in a lawn with a working sprinkler system are frustrating, and the usual response, running the zone longer, just drowns the areas that were already fine. Uneven sprinkler coverage almost always has a specific cause: heads too far apart, mismatched nozzles, the wrong pressure, sunken or tilted heads or spray blocked by plants. This guide shows how to measure coverage with a simple catch-cup test, diagnose the cause and fix it so the whole lawn gets the same amount of water.

For other repairs, see our sprinkler system repair guide.

Signs of uneven coverage

The pattern of the damage often hints at the cause.

• Brown arcs or strips in a regular pattern between heads.
• Soggy areas, moss or mushrooms close to some heads.
• Grass that greens up unevenly after fertilizing.
• Dry corners and edges.
• The temptation to increase run times every summer.

Common causes of uneven sprinkler coverage

Most lawns with patchy coverage have two or three of these at once, so check them all rather than stopping at the first one you find.

Why even coverage matters

Uneven watering forces a trade-off you should not have to make. To keep the driest spot green, you run the zone longer, which overwaters everywhere else. Overwatered areas develop shallow roots, disease, fungus and moss, while the dry areas still struggle in heat. Even coverage lets you water the whole lawn the right amount, typically using less water overall, and keeps turf uniform in color and density. It also reduces runoff into streets and storm drains.

Step 1: Watch every zone run

Run each zone and walk the area. Look for heads that do not pop up fully, tilt, spray into grass, mist, spray pavement or fail to reach their neighbors. Flag problems as you go. Fix obvious issues like clogged nozzles and broken heads before testing.

Step 2: Do a catch-cup test

This is the most useful single test you can do on a sprinkler system, and it costs almost nothing.

1. Place identical straight-sided containers, such as tuna cans or rain gauges, across one zone in a rough grid, including near heads, between heads and along edges.
2. Run the zone for a set time, such as 15 minutes for spray heads or 30 minutes for rotors.
3. Measure the depth of water in each container.
4. Compare the readings.

The test also tells you your zone's application rate, which helps you set run times. Our guide on how long to run a sprinkler for 1 inch explains the calculation.

Step 3: Check head spacing

Measure the distance between heads with a tape and compare it with the throw distance listed for each nozzle. For even coverage, each head should throw water all the way to the next head. This is called head-to-head coverage. If heads are spaced farther apart than their throw, dry bands form between them. Fixes include:

• Using nozzles with a longer throw, if pressure allows.
• Adding heads to fill gaps.
• Moving heads closer together where layout permits.

Step 4: Match nozzles and head types

Mismatched nozzles are one of the most common causes of patchy lawns, and one of the cheapest to fix. Within a zone, every head should apply water at roughly the same rate per square foot. This is called matched precipitation.

• Keep rotors and spray heads on separate zones. Spray heads apply water much faster.
• Match nozzles to arc. A half-circle head should usually have about half the flow of a full-circle head covering the same radius, and a quarter-circle about a quarter. Many nozzle sets are designed this way.
• Use the same brand and series where possible, since nozzle ratings vary between manufacturers.
• Consider rotary nozzles for spray zones, which apply water more slowly and evenly.

Step 5: Fix pressure problems

Each head type works best within a pressure range listed by the manufacturer.

Low pressure shortens throw and weakens spray, especially at the far end of a zone. Look for leaks, check that valves and the backflow device are fully open and avoid running too many heads on one zone. See low water pressure in a sprinkler system.

High pressure causes misting, which drifts and evaporates. Pressure-regulating spray bodies or a regulator on the supply line help.

Step 6: Raise and straighten heads

Head height problems are easy to miss because the head still sprays; it just does not reach as far. Heads that have sunk below the turf spray into the grass, and tilted heads throw unevenly. Dig around them, straighten and raise them so the top is flush with the soil. See how to raise a sprinkler head.

Step 7: Clear blocked spray

Even a small clump of tall grass right in front of a nozzle can create a dry wedge. Shrubs, flowers, tall grass, fences and trees can block or deflect spray. Trim plants around heads, use taller pop-ups in beds or relocate heads that cannot clear obstacles.

Step 8: Adjust arcs and radius

Small changes can make a big difference to coverage at the edges of each head's pattern. Make sure each head covers the area it should, without gaps or overspray. Our guide on adjusting a rotor sprinkler head walks through arc and radius settings.

Remember that grass and plants grow. A layout that worked when shrubs were small may now be blocked in several places, so walk the zones each spring.

Step 9: Retest and set run times

Keep your cup results; they make next year's check much faster. After making changes, repeat the catch-cup test. When readings are reasonably close, set run times based on the average depth so the zone delivers the amount of water the lawn needs. Even coverage often means you can shorten run times overall.

Using hose-end sprinklers evenly

If you water with hose-end sprinklers rather than an in-ground system, coverage is just as important. Oscillating sprinklers tend to put more water near the ends of their sweep, and impact sprinklers apply more near the head. To even things out:

• Move the sprinkler in a regular pattern so coverage areas overlap by about half.
• Run a catch-cup test for each sprinkler position to learn how long to leave it.
• Avoid placing the sprinkler so its pattern overlaps pavement.
• Use a hose timer so each position gets the same run time.

A simple yearly coverage routine

1. In early spring, run each zone and fix broken, tilted and sunken heads.
2. Clean nozzles and filter screens.
3. Run a catch-cup test on each zone.
4. Adjust arcs, radius and nozzles based on the results.
5. Set run times from the test.
6. Recheck in midsummer, when growth and heat reveal weak spots.

Is it the sprinklers or something else?

Not every brown patch is a coverage problem. Before changing heads, rule out:

• Grubs, which leave turf that lifts like a loose carpet.
• Disease, such as brown patch or dollar spot, which forms circular patterns.
• Dog urine, which leaves round dead spots with a green ring.
• Compacted soil, where water runs off before soaking in.
• Thatch, which sheds water and keeps roots shallow.
• Shallow soil over rock or construction debris, which dries out quickly.

A catch-cup test helps here too. If cups in the dry patch collect about as much water as elsewhere, the cause is probably not coverage.

Coverage tips for different lawn shapes

Long, narrow lawns are hard to cover evenly with spray heads. Strip nozzles along the edges or a single row of heads with matched patterns works better than heads placed randomly.

Curved beds and edges benefit from variable-arc nozzles that can be set to odd angles.

Large open lawns are best covered by rotors spaced head to head in a triangular or square grid.

Small, irregular lawns may need several short-throw spray heads with carefully matched nozzles.

Common mistakes

• Increasing run time instead of fixing coverage.
• Mixing rotors and spray heads on one zone.
• Replacing a broken head with a different brand or nozzle size.
• Lowering radius screws so far that streams turn to mist.
• Skipping a retest after adjustments.
• Ignoring grass growth that slowly blocks spray.

When to upgrade the system

If your heads are spaced too far apart and pressure is already maxed out, adjustments can only do so much. Adding heads, splitting an overloaded zone into two or upgrading to rotary nozzles may be the most practical fix. Our roundup of the best sprinkler watering systems for lawns compares components for upgrades.

Environmental factors

Even a well-designed system is affected by conditions outside your control. Plan around them.

• Wind distorts spray. Water early in the morning, when it is usually calmer.
• Slopes shed water downhill. Use cycle and soak scheduling so water infiltrates.
• Shade and sun change water needs. Put very different areas on separate zones if possible.
• Soil differences mean some areas dry faster even with even watering.

The EPA WaterSense program recommends irrigation audits, including catch-cup tests, to improve efficiency.

The bottom line

To fix uneven sprinkler coverage, watch each zone run, clean and repair obvious problems and run a catch-cup test to measure how evenly water is applied. Then correct head spacing for head-to-head coverage, match nozzles and keep rotors and sprays on separate zones, fix low or high pressure, raise and straighten sunken heads and clear blocked spray. Retest, set run times from the results and stop relying on longer cycles to cover dry spots.

Frequently Asked Questions